Pine Straw: A “New” Mulch for Missouri

Pine straw, the accumulation of naturally shed needles of pine trees, is an excellent landscape mulching material. It is commonly harvested in 20-30 pound bales and sold in the southeastern U.S., where it is the primary mulching material used in landscape plantings. However, loblolly pine, the predominant species used for pine straw plantations in the south, may not be tolerant to Missouri winters. Shortleaf, the only pine species native to Missouri, is not well suited to pine straw production because its needles are too short to bale.

That said, many sites in Missouri are suitable for pine straw production. Work is underway in the MU Center for Agroforestry to evaluate the potential of cold-tolerant selections of loblolly pine and pitch x loblolly hybrid pines for production of pine straw in Missouri. These trees have cold hardiness for Missouri with a similar needle length to loblolly.

Pine straw is a multi-million dollar industry in the U.S. A well-managed plantation in full production can gross up to $1,000 per acre from the sale of pine straw bales. While a tree can only give its bark once, it can give needles every year; pine straw production is sustainable agriculture. However, from a tree health standpoint, it is best to harvest only a portion of the plantation in a given year to allow trees to benefit from needle accumulation between harvests. Since pine straw is actually a leaf (needle), it benefits the landscape in much the same way as decomposing leaves benefit the forest floor by recycling nutrients and maintaining soil organic matter. In contrast, hardwood bark mulch, If overused, can cause a buildup of calcium and potassium in the soil, increasing pH and causing an imbalance in soil minerals that can interfere with nutrient uptake. The minerals in pine needles are balanced and therefore, their decomposition does not create an imbalance in the soil. Hardwood and pine bark mulch can wash away in a strong rain. Pine straw knits together and holds in place during heavy rain, helping to prevent soil erosion. Contrary to popular belief, mulching with pine straw does not make the underlying soil too acidic to grow most landscape plants.

The University of Missouri Center for Agroforestry is working toward creating a pine straw industry in the state of Missouri through research, product development and education, designed to encourage producers, retailers and consumers to adopt the use of this renewable, sustainable, natural mulch material. Numerous pine genotypes have been evaluated at the Horticulture and Agroforestry Research Center (HARC), in New Franklin, Mo for their potential for pine straw production. Ultimately the goal is to establish a seed orchard from trees shown to be superior. Then, Missourians will be able to use the seed created to plant their own pine straw plantations.

At present, Missourians who wish to try mulching with pine straw will have some difficulty locating vendors. Some nurseries in St. Louis, Kansas City and Columbia are selling pine straw. However, this is mostly being shipped in from suppliers in Florida. Hopefully, some of the Missouri landowners who have already planted hardy loblolly and pitch x loblolly hybrid pines will be harvesting needles in the not too distant future.

To read information about pine straw check out this web page from the Center for Agroforestry.
(by Christopher Starbuck, Associate Professor, MU Horticulture)